Sealed core for an absorbent article

ABSTRACT

An absorbent article is provided including a topsheet, a backsheet, and an absorbent core disposed between the topsheet and the backsheet. The core defines a wearer facing side oriented towards a wearer when the article is being worn and an opposed garment facing side. The core includes a storage layer that also defines a wearer facing side and an opposed garment facing side. The core further includes a first core wrap sheet covering the wearer facing side of the storage layer, and a second core wrap sheet covering the garment facing side of the storage layer. The first core wrap sheet is joined to the second core wrap sheet along at least one stripe of juncture. The stripe of juncture extends in at least one of the transversal and longitudinal directions.

FIELD OF THE INVENTION

The present invention relates to absorbent articles, such as diapers andsanitary napkins, and cores useful for such articles. More specifically,the present invention relates to absorbent cores for such articles andthe enveloping of such cores.

BACKGROUND OF THE INVENTION

Disposable absorbent articles are broadly available and consumers areused to a high performance for the collecting and retaining of menses(in the case of sanitary napkins or panty liners) or for the collectingand retaining urine and fecal material (in the case of e.g. disposablediapers). From such articles consumers expect a superior absorbencybehaviour and at the same time expect excellent the wearing comfort andthe dryness when being worn.

Often, such articles comprise multiple absorbent members, at least onemember being primarily designed to store liquid, and at least one othermember primarily designed to acquire and/or distribute liquid, themembers typically being encapsulated between a topsheet (on the wearerfacing side) and a backsheet (on the garment facing side).

In modern absorbent articles the absorbent core will typically comprisea super-absorbent material in combination with a fibrous material, forexample cellulose. In particular, the storage layer will be providedfrom a combination of such materials. It is important to maintain theintegrity of such absorbent core, both when the article is dry and whenthe article is wet, that means before use and in use. It is alsoimportant to prevent the escape of any of the absorbent materialsproviding the core, in particular the escape of super-absorbentmaterials, which are often provided in the form of particles. The escapeof super-absorbent materials from the core could ultimatively lead tocontact of such super-absorbent materials with the skin of the wearer.This phenomenon is known as gel on skin (as the super-absorbentmaterials are often also referred to as hydrogels). However, such gel onskin occurrences are considered undesirable as many consumers considerthe skin contact of such super-absorbent material to be unpleasant. Somerecent absorbent articles, especially disposable diapers, employrelatively open topsheet structures. These open topsheets promote theabsorbance or at least the adherence of high viscosity exudates, such asbowel movement. However, when it's specifically comes to gel on skinproblems, these open topsheet structures present a challenge, as they donot represent a highly effected barrier for super-absorbent particles,which may escape from the absorbent core of the absorbent article.

U.S. Pat. No. 4,573,986 (filed in 1984) discloses an early attempt forobviating lifting out of fibers and particulate matters from theabsorbent core of an absorbent garment. A wet-strength-tissue envelopeis disclosed in which the absorbent core is disposed and secured. Thewet-strength-tissue paper or a similar laminate is secured in face toface relation with the core by an open pattern of adhesive, which may,for example, comprise a fine pattern of globulettes of adhesive.Alternatively, a reticulated network of filaments of adhesives can beused.

EP 847 263 (filed in 1995) discloses a more recent core wrap material:Disclosed is a core wrap made from a fibrous non-woven web, preferably apolypropylene melt-blown non-woven material. This core wrap material maybe folded over on itself and then sealed using, for example, adhesives,heat and/or pressure. In this context, ultrasonic bonder,thermo-mechanically bonding means and adhesives are specificallydisclosed as suitable sealing means.

EP 1 088 537 (filed in 2000) discloses a highly water absorbent sheet.This absorbent sheet comprises fine cellulose fibers which provide afibrous network holding solid super-absorbent particles in position. Inorder to prevent the escaping of such super-absorbent particles, thedisclosed absorbent sheet relies on a hot-melt adhesive forming afurther fibrous network and covering the super-absorbent particles.

WO 00/64396 (filed in 2000) discloses yet a further approach forintegrity and immobilization enhancement for an absorbent member. Themethod comprises the application of a foamable movement obstructionagent to an absorbent member.

As to provide the desired absorbency to the article, at least thestorage member will typically comprise super-absorbent material, whichis admixed with the traditionally used pulp fiber material. Suchsuper-absorbent materials can absorb many times (e.g. 10, 20 or 30times) their own weight and are therefore very helpful when designing anarticle of improved fluid handling properties. Many recent productsemploy higher and higher concentrations of super-absorbent materials,that is concentrations in excess of 50% of the total weight of thestorage member. These products achieve a high absorbing capacity with avery thin storage member and are thereby typically overall thinproducts. While super-absorbent materials can store very large amountsof liquid, they are often not able to distribute the liquid from thepoint of impact to more remote areas of the absorbent article and toacquire the liquid as fast as it may be received by the article.

Hence, the prior art has disclosed various attempts to prevent theescaping of super-absorbent particles from the absorbent core. However,especially when it comes to absorbent cores with high concentrations ofsuper-absorbent material and the use of relatively open topsheetstructures, an even more efficient prevention of the escaping ofsuper-absorbent particles from the absorbent core is desirable.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, an absorbentarticle is provided that extends along a longitudinal axis and atransverse axis. The absorbent article includes a topsheet, a backsheet,and an absorbent core disposed between the topsheet and the backsheet.The core defines a wearer facing side oriented towards a wearer when thearticle is being worn and an opposed garment facing side. The coreincludes 1) a storage layer defining a wearer facing side and an opposedgarment facing side, 2) a first core wrap sheet covering the wearerfacing side of the storage layer, and 3) a second core wrap sheetcovering the garment facing side of the storage layer, wherein the firstcore wrap sheet is joined to the second core wrap sheet along at leastone stripe of juncture. The stripe of juncture extends in at least oneof the longitudinal and transversal directions. If the stripe ofjuncture extends longitudinally, the stripe of juncture comprises amicrofiber adhesive. If the stripe of juncture extends in thetransversal direction, the stripe of juncture provides a bond strengthof at least 1 N/cm between the first core wrap sheet and a second corewrap sheet as measured as tensile strength in the longitudinal directionand comprises a microfiber adhesive.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims pointing out anddistinctly claiming the present invention, it is believed the same willbe better understood by the following drawings taken in conjunction withthe accompanying specification wherein like components are given thesame reference number.

FIG. 1 is a top plan view of a disposable diaper, with the upper layerspartially cut away;

FIG. 2 is a cross-sectional view of the disposable diaper shown in FIG.1; and

FIG. 3 is a top plan view of the storage layer comprised by theabsorbent core of a disposable diaper as shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION Definitions

As used herein, the following terms have the following meanings:

“Absorbent article” refers to devices that absorb and contain liquid,and more specifically, refers to devices that are placed against or inproximity to the body of the wearer to absorb and contain the variousexudates discharged from the body. Absorbent articles include but arenot limited to diapers, adult incontinent briefs, training pants, diaperholders and liners, sanitary napkins and the like. Absorbent articlesalso include wipes, such as household cleaning wipes, baby wipes, andthe like.

“Disposable” is used herein to describe articles that are generally notintended to be laundered or otherwise restored or reused i.e., they areintended to be discarded after a single use and, preferably, to berecycled, composted or otherwise disposed of in an environmentallycompatible manner.

“Disposed” is used to mean that an element(s) is formed (joined andpositioned) in a particular place or position as a unitary structurewith other elements or as a separate element joined to another element.

“Diaper” refers to an absorbent article generally worn by infants andincontinent persons about the lower torso.

The terms “thickness” and “caliper” are used herein interchangeably.

“Attached” or “Joined” encompasses configurations whereby an element isdirectly secured to another element by affixing the element directly tothe other element, and configurations whereby an element is indirectlysecured to another element by affixing the element to intermediatemember(s) which in turn are affixed to the other element.

“Comprise,” “comprising,” and “comprises” is an open ended term thatspecifies the presence of what follows e.g. a component but does notpreclude the presents of other features, elements, steps or componentsknown in the art, or disclosed herein.

The term “hydrophilic” describes fibers or surfaces of fibers, which arewettable by aqueous fluids (e.g. aqueous body fluids) deposited on thesefibers. Hydrophilicity and wettability are typically defined in terms ofcontact angle and the strike through time of the fluids, for examplethrough a nonwoven fabric. This is discussed in detail in the AmericanChemical Society publication entitled “Contact angle, wettability andadhesion”, edited by Robert F. Gould (Copyright 1964). A fiber orsurface of a fiber is said to be wetted by a fluid (i.e. hydrophilic)when either the contact angle between the fluid and the fiber, or itssurface, is less than 90°, or when the fluid tends to spreadspontaneously across the surface of the fiber, both conditions arenormally co-existing. Conversely, a fiber or surface of the fiber isconsidered to be hydrophobic if the contact angle is greater than 90°and the fluid does not spread spontaneously across the surface of thefiber.

The terms “fiber” and “filament” are used interchangeably.

The terms “nonwoven”, “nonwoven fabric” and “nonwoven web” are usedinterchangeable.

The disposable article 20 has two centerlines, a longitudinal centerline100 and a transverse centerline 110.

The term “longitudinal”, as used herein, refers to a line, axis ordirection in the plane of the disposable article 20 that is generallyaligned with (e.g., approximately parallel to) a vertical plane whichbisects a standing wearer into left and right body halves when thedisposable article 20 is worn.

The terms “transverse” or “lateral” as used herein, are interchangeable,and refer to a line, axis or direction which lies in the plane of thedisposable article 20 that is generally perpendicular to thelongitudinal direction.

Absorbent Articles

FIG. 1 is a plan view of a diaper 20 as a preferred embodiment of anabsorbent article according to the present invention. The diaper isshown in its flat out, uncontracted state (i.e., without elastic inducedcontraction). Portions of the structure are cut away to more clearlyshow the underlying structure of the diaper 20. The portion of thediaper 20 that contacts a wearer is facing the viewer. The chassis 22 ofthe diaper 20 in FIG. 1 comprises the main body of the diaper 20. Thechassis 22 comprises an outer covering including a liquid pervioustopsheet 24 and/or a liquid impervious backsheet 26. The chassis mayalso include most or all of the absorbent core 28 encased between thetopsheet 24 and the backsheet 26. The chassis preferably furtherincludes side panels 30, leg cuffs 32 and a waist feature 34. The legcuffs and the waist feature typically comprise elastic members 33. Oneend portion of the diaper 20 is configured as the front waist region 36of the diaper 20. The opposite end portion is configured as the rearwaist region 38 of the diaper 20. An intermediate portion of the diaper20 is configured as the crotch region 37, which extends longitudinallybetween the front and rear waist regions 36 and 38. The crotch region 37is that portion of the diaper 20 which, when the diaper 20 is worn, isgenerally positioned between the wearer's legs. The waist regions 36 and38 may include a fastening system comprising fastening members 40preferably attached to the rear waist region 38 and a landing zone 42attached to the front waist region 36. The diaper 20 has a longitudinalaxis and centerline 100 and a transverse axis and centerline 110. Theperiphery of the diaper 20 is defined by the outer edges of the diaper20 in which the longitudinal edges 44 run generally parallel to thelongitudinal axis 100 of the diaper 20 and the end edges 46 rungenerally parallel to the transverse axis 110 of the diaper 20.

For unitary absorbent articles, the chassis 22 comprises the mainstructure of the diaper with other features added to form the compositediaper structure. While the topsheet 24, the backsheet 26, and theabsorbent core 28 may be assembled in a variety of well-knownconfigurations, preferred diaper configurations are described generallyin U.S. Pat. No. 5,569,234 entitled “Disposable Pull-On Pant” issued toBuell et al. on Oct. 29, 1996; and U.S. Pat. No. 6,004,306 entitled“Absorbent Article With Multi-Directional Extensible Side Panels” issuedto Robles et al. on Dec. 21, 1999.

The topsheet 24 in FIG. 1 may be fully or partially elasticized or maybe foreshortened to provide a void space between the topsheet 24 and theabsorbent core 28. Exemplary structures including elasticized orforeshortened topsheets are described in more detail in U.S. Pat. No.5,037,416 entitled “Disposable Absorbent Article Having ElasticallyExtensible Topsheet” issued to Allen et al. on Aug. 6, 1991; and U.S.Pat. No. 5,269,775 entitled “Trisection Topsheets for DisposableAbsorbent Articles and Disposable Absorbent Articles Having SuchTrisection Topsheets” issued to Freeland et al. on Dec. 14, 1993.

The backsheet 26 in FIG. 1 is generally the portion of the diaper 20positioned with the absorbent core 28 between the backsheet 26 and thetopsheet 24. The backsheet 26 may be joined with the topsheet 24. Thebacksheet 26 prevents the exudates absorbed by the absorbent core 28 andcontained within the article 20 from soiling other external articlesthat may contact the diaper 20, such as bed sheets and undergarments. Inpreferred embodiments, the backsheet 26 is substantially impervious toliquids (e.g., urine) and comprises a laminate of a nonwoven and a thinplastic film such as a thermoplastic film having a thickness of about0.012 mm (0.5 mil) to about 0.051 mm (2.0 mils). Suitable backsheetfilms include those manufactured by Tredegar Industries Inc. of TerreHaute, Ind. and sold under the trade names X15306, X10962, and X10964.Other suitable backsheet materials may include breathable materials thatpermit vapors to escape from the diaper 20 while still preventingexudates from passing through the backsheet 26. Exemplary breathablematerials may include materials such as woven webs, nonwoven webs,composite materials such as film-coated nonwoven webs, and microporousfilms such as manufactured by Mitsui Toatsu Co., of Japan under thedesignation ESPOIR NO and by EXXON Chemical Co., of Bay City, Tex.,under the designation EXXAIRE.

The absorbent core 28 in FIG. 1 generally is disposed between thetopsheet 24 and the backsheet 26. The absorbent core 28 may comprise anyabsorbent material that is generally compressible, conformable,non-irritating to the wearer's skin, and capable of absorbing andretaining liquids such as urine and other certain body exudates. Theabsorbent core 28 may comprise a wide variety of liquid-absorbentmaterials commonly used in disposable diapers and other absorbentarticles such as comminuted wood pulp, which is generally referred to asair felt. Examples of other suitable absorbent materials include crepedcellulose wadding; melt blown polymers, including co-form; chemicallystiffened, modified or cross-linked cellulosic fibers; tissue, includingtissue wraps and tissue laminates, absorbent foams, absorbent sponges,superabsorbent polymers, absorbent gelling materials, or any other knownabsorbent material or combinations of materials. The absorbent core mayfurther comprise minor amounts (typically less than 10%) of non-liquidabsorbent materials, such as adhesives, waxes, oils and the like.

Exemplary absorbent structures for use as the absorbent assemblies aredescribed in U.S. Pat. No. 4,834,735, entitled “High Density AbsorbentMembers Having Lower Density and Lower Basis Weight Acquisition Zones”,issued to Alemany et al. on May 30, 1989; and U.S. Pat. No. 5,625,222entitled “Absorbent Foam Materials For Aqueous Fluids Made From highInternal Phase Emulsions Having Very High Water-To-Oil Ratios” issued toDesMarais et al. on Jul. 22, 1997.

The diaper 20 may also include such other features as are known in theart including front and rear ear panels, waist cap features, elasticsand the like to provide better fit, containment and aestheticcharacteristics. Such additional features are well known in the art andare described in U.S. Pat. No. 3,860,003 entitled “Contractable sideportions for disposable diaper” issued to Buell et al. on Jan. 14, 1975and U.S. Pat. No. 5,151,092 entitled “Absorbent article with dynamicelastic waist feature having a predisposed resilient flexural hinge”issued to Buell et al. on Sep. 29, 1992.

In order to keep the diaper 20 in place about the wearer, the waistregions 36 and 38 may include a fastening system comprising fasteningmembers 40 preferably attached to the rear waist region 38. In apreferred embodiment the fastening system further comprises a landingzone 42 attached to the front waist region 36. The fastening member isattached to the front waist region 36, preferably to the landing zone 42to form leg openings and an article waist.

Diapers 20 according to the present invention may be provided with are-closable fastening system or may alternatively be provided in theform of pant-type diapers.

The fastening system and any component thereof may include any materialsuitable for such a use, including but not limited to plastics, films,foams, nonwoven webs, woven webs, paper, laminates, fiber reinforcedplastics and the like, or combinations thereof. It may be preferablethat the materials making up the fastening device be flexible. Theflexibility is designed to allow the fastening system to conform to theshape of the body and thus, reduces the likelihood that the fasteningsystem will irritate or injure the wearer's skin.

FIG. 2 shows a cross-sectional view of FIG. 1 taken in the transverseaxis 110. Starting from the wearer facing side the diaper comprises thetopsheet 24, the components of the absorbent core 28, and the backsheet26. The absorbent core preferably comprises an acquisition system 50,which comprises an upper acquisition layer 52 facing towards the wearerand a lower acquisition layer 54. In one preferred embodiment the upperacquisition layer comprises a nonwoven fabric whereas the loweracquisition layer preferably comprises a mixture of chemicallystiffened, twisted and curled fibers, high surface area fibers andthermoplastic binding fibers. In another preferred embodiment bothacquisition layers are provided from a non-woven material, which ispreferably hydrophilic. The acquisition layer preferably is in directcontact with the storage layer 60.

The storage layer 60 is preferably wrapped by a core wrap material. Inone preferred embodiment the core wrap material comprises a first corewrap layer 56 (top layer) and a second core wrap layer 58 (bottomlayer). The first core wrap layer 56 and the second core wrap layer 58can be provided from a non-woven material. One preferred material is aso-called SMS material, comprising a spunbonded, a melt-blown and afurther spunbonded layer. The first core wrap layer 56 and the secondcore wrap layer 58 may be provided from two or more separate sheets ofmaterials or they may be alternatively provided from a unitary sheet ofmaterial. Such a unitary sheet of material may be wrapped around thestorage layer 60, e.g. in a C-fold. The first core wrap layer 56 and thesecond core wrap layer 58 may also be joined to each other, preferablyalong their periphery. In one preferred option both layers are joinedalong their longitudinal peripheries, in other embodiments they arejoined along the transversal peripheries, or along the longitudinal andthe transversal peripheries. The joining can be achieved my multiplemeans well known in the art, eg. by adhesive means, using a continuousor a discontinuous pattern, and preferably a linear or curvilinearpattern.

The storage layer 60 typically comprises fibrous materials, mixed withsuperabsorbent, absorbent gelling materials. Other materials describedabove as suitable for the absorbent core 28 may also be comprised.Preferred storage layer according to the present invention may comprisea superabsorbent material in an amount corresponding to at least 30%, orat least 40%, or at least 50%, or at least 60%, or at least 70%, or atleast 80% or at least 90% of the total weight of the storage layer.

A upper liquid acquisition layer 52 useful in a diaper according to thepresent invention may comprise any of the nonwoven fabrics describedbelow. A preferred liquid acquisition layer 52 comprises a bindercomprising a styrene-butadiene latex binder. Preferably, thestyrene-butadiene latex binder has a carboxylation level of at least10%, preferably at least 12%. Preferably, the upper liquid acquisitionlayer 52 comprises polyester fibers and the liquid acquisition layercomprises 20 to 40 weight percent of styrene-butadiene latex binder, and60 to 80 weight percent of said polyester fibers. Even more preferably,the polyester fibers comprise 20 to 80 weight percent of a first type offibers, and 20 to 80 weight percent of a second type of fibers, thesecond type of fibers comprising spiral-crimp fibers. Highly preferredare upper liquid acquisition layers wherein the first type of fibersexhibits a flat crimp and wherein the second type of fibers compriseshollow chemically homogeneous bi-component fibers. Also highly preferredare any upper liquid acquisition layers wherein the polyester fibers arecarded to form a nonwoven.

Preferred acquisition systems may also comprise superabsorbentmaterials. Such acquisition systems may also comprise a singleacquisition layer or multiple acquisition layers. Where multipleacquisition layers are comprised any of these layer may comprisesuperabsorbent materials. Such superabsorbent material may be comprisedin an amount corresponding to at least 30%, or at least 50% or at least70%, at times even in an amount of 100% of the total weight of therespective acquisition layer.

Nonwoven Fabrics

A nonwoven fabric is a manufactured sheet, web or batt of directionallyor randomly orientated fibers, bonded by friction, and/or cohesionand/or adhesion, excluding paper and products which are woven, knitted,tufted, stitch-bonded incorporating binding yarns or filaments, orfelted by wet-milling, whether or not additionally needled.

The fibres may be of natural or man-made origin. They may be staple orcontinuous filaments or be formed in situ.

Nonwoven fabrics can be formed by many processes such as meltblowing,spunbonding, carding. The basis weight of nonwoven fabrics is usuallyexpressed in grams per square meter (gsm).

Commercially available fibers have diameters ranging from less thanabout 0.001 mm to more than about 0.2 mm and they come in severaldifferent forms: short fibers (known as staple, or chopped), continuoussingle fibers (filaments or monofilaments), untwisted bundles ofcontinuous filaments (tow), and twisted bundles of continuous filaments(yarn). Fibers are classified according to their origin, chemicalstructure, or both. They can be braided into ropes and cordage, madeinto felts (also called nonwovens or nonwoven fabrics), woven or knittedinto textile fabrics, or, in the case of high-strength fibers, used asreinforcements in composites—that is, products made of two or moredifferent materials.

The nonwoven fabrics may comprise fibers made by nature (naturalfibers), made by man (synthetic or man-made), or combinations thereof.Example natural fibers include but are not limited to: animal fiberssuch as wool, silk, fur, and hair; vegetable fibers such as cellulose,cotton, flax, linen, and hemp; and certain naturally occurring mineralfibers. Synthetic fibers can be derived from natural fibers or not.Example synthetic fibers, which are derived from natural fibers includebut are not limited to rayon and lyocell, both of which are derived fromcellulose, a natural polysaccharide fiber. Synthetic fibers, which arenot derived from natural fibers can be derived from other naturalsources or from mineral sources. Example synthetic fibers not derivedfrom natural sources include but are not limited to polysaccharides suchas starch. Example fibers from mineral sources include but are notlimited to polyolefin fibers such as polypropylene, polyethylene fibersand polyester, which are derived from petroleum, and silicate fiberssuch as glass and asbestos.

Nonwoven webs can be formed by direct extrusion processes during whichthe fibers and webs are formed at about the same point in time, or bypreformed fibers, which can be laid into webs at a distinctly subsequentpoint in time. Example direct extrusion processes include but are notlimited to: spunbonding, meltblowing, solvent spinning, electrospinning,and combinations thereof typically forming layers.

Example “laying” processes include wetlaying and drylaying. Exampledrylaying processes include but are not limited to airlaying, carding,and combinations thereof typically forming layers. Combinations of theabove processes yield nonwovens commonly called hybrids or composites.Example combinations include but are not limited tospunbond-meltblown-spunbond (SMS), spunbond-carded (SC),spunbond-airlaid (SA), meltblown-airlaid (MA), and combinations thereof,typically in layers. Combinations which include direct extrusion can becombined at about the same point in time as the direct extrusion process(e.g., spinform and coform for SA and MA), or at a subsequent point intime. In the above examples, one or more individual layers can becreated by each process. For instance, SMS can mean a three layer, ‘sms’web, a five layer ‘ssmms’ web, or any reasonable variation thereofwherein the lower case letters designate individual layers and the uppercase letters designate the compilation of similar, adjacent layers.

The fibers in a nonwoven web are typically joined to one or moreadjacent fibers at some of the overlapping junctions. This includesjoining fibers within each layer and joining fibers between layers whenthere is more than one layer. Fibers can be joined by mechanicalentanglement, by chemical bond or by combinations thereof. Fibers canalso be joined by heat-bonding, which comprises techniques such asthrough-air bonding and thermobonding by use of heated calendar rolls.

Preferred Topsheets

Preferred topsheets for use with the present invention are compliant,soft feeling, and non-irritating to the wearer's skin. Further, thetopsheet 24 should be liquid pervious, permitting liquids (e.g., urine)to readily penetrate through its thickness. A suitable topsheet 24 maybe manufactured from a wide range of materials, such as porous foams;reticulated foams; apertured plastic films; or woven or nonwoven webs ofnatural fibers (e.g., wood or cotton fibers), synthetic fibers (e.g.,polyester or polypropylene fibers), or a combination of natural andsynthetic fibers. Preferably, the topsheet 24 is made of a hydrophobicmaterial to isolate the wearer's skin from liquids contained in theabsorbent core 28. Alternatively, the topsheet 24 may be surfactanttreated to make it hydrophilic.

The topsheet 24 preferably has a plurality of apertures with aneffective aperture size of at least 0.2 square millimeters, morepreferably, the plurality of apertures have an effective aperture sizeof at least 0.5 square millimeters, even more preferably, the pluralityof apertures have an effective aperture size of at least 1.0 squaremillimeters, and most preferably, the plurality of apertures have aneffective aperture size of at least 2.0 square millimeters. Effectiveapertures are those which have a gray level of 18 or less on a standardgray level scale of 0-255, under the image acquisition parametersdescribed in EP 1 032 336 B1. An aperture having a material free area ofx square millimeters is to be understood as having an effective aperturesize of at least x square millimeters.

The topsheet 24 preferably has an effective open area of at least 15percent, more preferably the topsheet has an effective open area of atleast 20 percent, even more preferably, the topsheet has an effectiveopen area of at least 25 percent, and most preferably the topsheet hasan effective open area of at least 30 percent. Preferably, at least 50%or at least 75% of the topsheet surface are provided with suchapertures.

Preferred Absorbent Cores

All of the above described fibers and manufacturing techniques can beuseful for providing core wrap sheets according to the presentinvention.

Preferred core wrap sheets are made of a hydrophilic material to promoterapid transfer of liquids (e.g. urine) through at least the first corewrap sheet. If such core wrap sheets are made of a hydrophobic material,such material can be treated to be hydrophilic, for example by treatmentwith a surfactant.

There are multiple ways to envelope an absorbent core using a first corewrap sheet and a second core wrap sheet, all of which are within thescope of the present invention. For example, two separate wrap sheetsmay be used, the first core wrap sheet covering the wearer facing sideof the core and the second core wrap sheet covering the garment facingsided of the core. Both wrap sheets can then be joined alonglongitudinally extending stripes of juncture, one stripe of juncture toeach side of the absorbent core. Alternatively, the first core wrapsheet can be integral with the second core wrap sheet and be providedfrom one and the same sheet of material. Then, only one longitudinallyextending stripe of juncture needs to be employed as to achieve theenveloping. Such stripe of juncture can either be of the wearer facingside of the core, or on the garment facing side of the core on eitherlateral side of the core. The overlapping ends of the wrap sheetmaterial, which are to be joined by said stripe of juncture, can bearranged as to create a butt seal or can be arranged as to create anoverlapping seal. Both an overlapping seal and a butt seal can be joinedusing a stripe of juncture in accordance to the present invention.

Referring to FIG. 3, the core wrap sheets may be joined by alongitudinally extending stripe of juncture 74 (for example a side seal)and/or by a transversally extending stripe of juncture 72, which istypically positioned either at the front end of the absorbent core or atthe rear end of the absorbent core or at both ends of the absorbentcore. Such a transversally extending stripe of juncture can be providedby the same means as a longitudinally extending stripe of juncture.

The stripe of juncture may comprise different elements having a bondingfunction, herein referred as bonding elements. For example, bondingelements can be provided by adhesive bonding, by thermo-mechanicalbonding, by ultrasonic bonding and the like. According to the presentinvention at least some bonding elements comprise a microfiber adhesive.The area of a rectangle comprising all bonding elements comprising amicrofiber adhesive of the stripe of juncture is herein referred to asthe total area of the stripe of juncture. According to the presentinvention, however, the stripe of juncture also comprises an open area.Open area, as used herein, denotes an area where no bonding elements arepresent.

According to the present invention, the microfiber adhesive preferablycomprises microfibers having a diameter of 10 micrometer to 300micrometer, preferably 20 micrometer to 50 micrometer. A stripe ofjuncture comprising microfibers can be created by meltblown spraying,spiral spraying, or omega spraying.

Generally, in accordance with the present invention, stripes of juncturehaving an open area of at least 20%, or at least 30%, or at least 40%,or at least 50%, or at least 60%, or at least 70%, or at least 80%, orat least 90% of their total area are preferred. However, the open areashould not be more than 95% of the total area as to ensure reliablebonding.

Core wrap sheets according to the present invention are preferablyprovided in the form of non-woven webs. More preferably, they areprovided from polyolefin, more preferably from polypropylene. Preferredcore wrap sheets have a basis weight from 3 gram per m² to 50 gram perm², more preferably from 5 gram per m² to 30 gram per m², preferablyfrom 8 gram per m² to 15 gram m².

The stripe of juncture will provide a certain bond strength between thecore wrap sheets. The stripe of junction will have its largest extensionin a first direction. The bond strength between the core wrap sheets, asused herein, is to be understood as the tensile strength in a seconddirection which is perpendicular to the first direction and within theplane defined by the core wrap sheets. To test tensile strength a testspecimen of 2.54 cm (1 inch) width is cut at a representative (typicallycentral) position by two cutting lines oriented in the second direction.Tensile strength is then measured using this test specimen of materialin accordance with ASTM method D 1876-01, which is modified as follows:The specimen length is 60 mm and unbonded ends of 10 mm length are usedfor clamping in the grips of the testing machine (see paragraph 5.2 of D1876-01). The portions of the first and second core wrap sheet formingpart of the specimen are used as flexible adherends (see paragraph 5.1of D 1876-01). Further, tensile strength is reported (in units of Newtondivided by centimeter specimen width; N/cm) as the maximum value of theobtained autographic curve (see paragraph 8.1 of D 1876-01).

According to the present invention the stripe of juncture providespreferably a bond strength of at least 0.5 N/cm between the first corewrap sheet (56) and a second core wrap sheet (58). According to thepresent invention in particular a stripe of juncture oriented in thetransversal direction should will this bond strength. Preferably thestripe of juncture provides a bond strength of at least 1.0 N/cm or 1.5N/cm or 2 N/cm or 3 N/cm.

Without wishing to be bound by theory, it seems particularly beneficialto have stripes of juncture which comprise microfibers and whichpreferably comprise a large open area. It appears that the occurrence ofthe gel-on-skin phenomenon is in part caused by super-absorbentparticles which in the process of manufacturing are captured within sucha line of junction. When a stripe of juncture is provided by continuousadhesive application, the superabsorbent material is limited in itsability to swell by being confined by the adhesive providing the stripeof juncture. However, the super-absorbent particle is likely to swellonce the article is in use and receives liquid. When this swelling ishighly restricted by the presence of adhesive, the swelling forces aretypically high enough to allow swelling in the direction of the corewrap sheets. These core wrap sheets are typically provided by non-wovenmaterials or tissue materials or similar materials which are relativelyweek. Hence, wherever the stripe of juncture itself does not providesufficient open or yielding space to accommodate the swelling ofsuper-absorbent particles, such particles will expand in the directionof the core wrap sheets. Therefore, they are likely to escape throughthe core wrap sheets, often also causing damage to the core wrap sheets.This escaping of super-absorbent material from the core and especiallyout of the areas of the stripes of juncture appears to noticeablycontribute to occurrences of gel-on-skin. If, however, in accordancewith the present invention a stripe of juncture comprising microfibersis applied, these microfibers present only little resistance to swellingfor the super-absorbent particles. In one aspect, individual microfibersmay yield to expanding superabsorbent particles as they are relativelyelastic, in a further aspect individual fibers may yield to expandingsuperabsorbent particles as they are relatively weak and break easily,and in a yet further aspect there will often be enough free spacebetween neighboring microfibers which provides room for swelling. Hence,the adhesive will either find a sufficient open area within the stripeof juncture to allow for swelling without exerting any pressure againstthe wrap sheets and against surrounding adhesive material or the overallsurrounding adhesive material will be elastic enough as to allow forswelling within the stripes of juncture while no or very little pressureis exerted towards the core wrap sheets.

In view of these considerations it seems best to select the dimension ofthe bonding elements and of the areas free of bonding elements in viewof the size of the super-absorbent particles which could escape from theabsorbent core (28). The value to be considered specifically is the meandiameter of the super-absorbent particles.

The mean diameter is to be determined using EDANA method 420.2-02entitled “Particle size distribution”. This EDANA method is a sievingmethod and reports the mass fraction in percent for each particle sizefraction remaining on the different sieves employed. Based on thisreport the mean diameter is calculated according to ASTM test method D1921-96, namely paragraph 13 thereof entitled “Analysis of ParticleDistribution”.

The spaces free of bonding elements will have a smallest dimension (thatis the smallest free width in any direction). According to the presentinvention this smallest dimension preferably is at least 0.5 times saidmean diameter (herein “MD”). More preferably, the smallest dimension isfrom 0.5 to 3 times the MD, more preferably from 0.5 to 2 times the MD,most preferably from 0.8 to 1.2 times the MD.

Hence, the stripes of juncture according to the present inventionprovide a sufficient bond strength on a macro level (when looking at theperformance of the overall absorbent article), but at the same timesufficient weakness and swelling space on a micro level (when looking atthe environment of single particles of super-absorbent material).

All documents cited in the Detailed Description of the Invention are, inrelevant part, incorporated herein by reference; the citation of anydocument is not to be construed as an admission that it is prior artwith respect to the present invention.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. An absorbent article extending along alongitudinal axis and a transverse axis, the absorbent articlecomprising: a topsheet; a backsheet; and an absorbent core disposedbetween the topsheet and the backsheet, the core defining a wearerfacing side oriented towards a wearer when the article is being worn andan opposed garment facing side, wherein the core includes 1) a storagelayer comprising a wearer facing side and an opposed garment facingside, 2) a first core wrap sheet covering the wearer facing side of thestorage layer, and 3) a second core wrap sheet covering the garmentfacing side of the storage layer, wherein the first core wrap sheet isjoined to the second core wrap sheet along at least one stripe ofjuncture; wherein the stripe of juncture extends in at least one of thelongitudinal and transversal directions, and wherein the stripe ofjuncture comprises a microfiber adhesive.
 2. The absorbent article asrecited in claim 1, wherein the microfibers of the microfiber adhesivehave a diameter of about 10 micrometers to about 300 micrometers.
 3. Theabsorbent article as recited in claim 1, wherein the stripe of junctureis created by meltblown spraying, spiral spraying, or omega spraying. 4.The absorbent article as recited in claim 1, wherein the stripe ofjuncture comprises an open area from about 30% to about 95% of the totalarea.
 5. The absorbent article as recited in claim 1, comprisingsuperabsorbent particles having a mean diameter.
 6. The absorbentarticle as recited in claim 5, wherein the stripe of juncture comprisesspaces free of the microfiber adhesive, the spaces having a smallestdimension, and wherein the smallest dimension is at least 0.5 times themean diameter.
 7. The absorbent article as recited in claim 1, whereinat least the first core wrap sheet or the second core wrap sheet has abasis weight from about 3 gram per m² to about 50 gram per m².
 8. Theabsorbent article as recited in claim 1, wherein the topsheet comprisesa plurality of pores having an effective aperture size of at least 2.0square millimeters.
 9. The absorbent article as recited in claim 1,wherein the topsheet is liquid pervious.
 10. The absorbent article asrecited in claim 1, wherein the backsheet is liquid impervious.
 11. Theabsorbent article as recited in claim 1, wherein the storage layercomprises superabsorbent material, and wherein the storage layer is atleast 30% superabsorbent material by total weight of the storage layer.12. The absorbent article as recited in claim 1, wherein the storagelayer comprises superabsorbent material, and wherein the storage layeris at least 80% superabsorbent material by total weight of the storagelayer.
 13. The absorbent article as recited in claim 1, wherein thefirst and second core wrap sheets together form a C-wrap around at leasta portion of the storage layer.
 14. The absorbent article as recited inclaim 1, wherein the stripe of juncture is continuous.
 15. The absorbentarticle as recited in claim 1, wherein the stripe of juncture isdiscontinuous.
 16. The absorbent article as recited in claim 1, whereinthe stripe of juncture is linear.
 17. The absorbent article as recitedin claim 1, wherein the stripe of juncture is non-linear.
 18. Theabsorbent article as recited in claim 1, wherein the stripe of junctureis linear and continuous.
 19. The absorbent article as recited in claim1, wherein the stripe of juncture is linear and discontinuous.
 20. Theabsorbent article as recited in claim 1, wherein the stripe of junctureis curvilinear.
 21. The absorbent article as recited in claim 1, whereinthe stripe of juncture is curvilinear and continuous.
 22. The absorbentarticle as recited in claim 1, wherein the stripe of juncture iscurvilinear and discontinuous.
 23. The absorbent article as recited inclaim 1, comprising an acquisition system positioned at least partiallyintermediate the topsheet and the absorbent core.
 24. The absorbentarticle as recited in claim 23, wherein the acquisition system comprisesa first layer and a second layer.
 25. The absorbent article as recitedin claim 1, comprising a second stripe of juncture joining the firstcore wrap sheet and the second core wrap sheet and that extends in atleast one of the longitudinal and transversal directions.
 26. Theabsorbent article as recited in claim 1, wherein the stripe of junctureextends in the longitudinal direction, comprising a second stripe ofjuncture joining the first core wrap sheet and the second core wrapsheet and that extends in the transversal direction.
 27. The absorbentarticle as recited in claim 1, comprising: a second stripe of juncturejoining the first core wrap sheet and the second core wrap sheet andthat extends in at least one of the longitudinal and transversaldirections; and a third stripe of juncture joining the first core wrapsheet and the second core wrap sheet and that extends in at least one ofthe longitudinal and transversal directions.
 28. The absorbent articleas recited in claim 27, comprising at least a fourth stripe of juncturejoining the first core wrap sheet and the second core wrap sheet andthat extends in at least one of the longitudinal and transversaldirections.
 29. The absorbent article as recited in claim 1, wherein thefirst core wrap sheet comprises a nonwoven material, and wherein thesecond core wrap sheet comprises a nonwoven material.
 30. The absorbentarticle as recited in claim 1, wherein the stripe of juncture has a bondstrength of at least 0.5N/cm between the first core wrap sheet and thesecond core wrap sheet.
 31. The absorbent article as recited in claim 1,wherein the stripe of juncture is provided by continuous adhesiveapplication.
 32. The absorbent article as recited in claim 1, whereinthe absorbent article comprises a diaper or a training pant.
 33. Theabsorbent article as recited in claim 1, wherein the absorbent articlecomprises a sanitary napkin.
 34. The absorbent article as recited inclaim 1, comprising a leg cuff and a fastening system.
 35. The absorbentarticle as recited in claim 1, wherein the absorbent core comprisescomminuted wood pulp.
 36. The absorbent article as recited in claim 1,wherein the storage layer comprises a fibrous material and asuperabsorbent material.
 37. The absorbent article as recited in claim1, comprising an acquisition system comprising superabsorbent materials.38. The absorbent article as recited in claim 1, wherein the stripe ofjuncture comprises bonding elements.